Who Watches the Watchers? (2): Self-cleaning Ovens

But can he bake a cherry pie?
One of our engineers told us that he received a call from his wife to clean the oven while she was out running errands. He relayed the orders to his son to start the oven’s self-cleaning mode. The son followed the orders dutifully but didn’t check the oven to see whether anything was stored inside. A short while later, smoke began pouring from the oven and the kitchen glowed from the light of the plastic cutting board burning inside.

Our engineer tried to turn the oven off but discovered that once the self-cleaning mode had been started, it couldn’t be stopped. Quick thinking prevailed—he went to the circuit breaker box and shut off the power. The oven, however, remained locked and the cutting board continued burning. It took the local fire department to pull the range out of kitchen and put it the driveway for the fire to finally burn out. Even then, the door could not be opened until the oven had cooled down.

That’s probably the last time our colleague will be asked to clean the oven. And it left us wondering why there’s no emergency override that would shut down the self-cleaning cycle.

I am so frightened of the commitment of the self-clean cycle that I’ve never used it for any oven. I just move houses when the oven gets too dirty. (I’m kidding, but it’s close to the truth.) I’m also scared of anything that hot being inside my house without being inside my chimney.

The reason ovens lock during a self-clean is temperature: it’s getting hot enough in there to burn away residue and you don’t want to accidentally open the door and be blasted. However, I can’t think of any reasons not to stop it mid-clean and have it remain locked until it cools down enough to be safe. My best guess is that older ovens were built with no way to sense temperature (the earliest ovens had an analog dial that operated in an open-loop system – you had to measure the temperature yourself and turn it up or down accordingly.) With no way to sense that the oven cooled sufficiently, the only way to be safe is to lock it until the cycle ended and a cool down time passed.

We’ve had closed-loop ovens that sense their own heat levels for a while now, so my second best guess is that the ovens still locked due to tradition. Some ovens have sensors specific to the cleaning cycle to shorten the self-clean time (though no mention is made of an emergency stop). Feedback can be a wonderful thing.